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List: kde-core-devel
Subject: Re: Review Request: Fix a VLC crash by delaying object deletion to avoid invalid access by QtDBus
From: "Dawit Alemayehu" <adawit () kde ! org>
Date: 2012-01-30 6:35:07
Message-ID: 20120130063507.28817.15242 () vidsolbach ! de
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This is an automatically generated e-mail. To reply, visit:
http://git.reviewboard.kde.org/r/100577/
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(Updated Jan. 30, 2012, 6:35 a.m.)
Review request for kdelibs and Thiago Macieira.
Changes
-------
Bring back an updated version of this patch since this crash can be reproduced using \
Qt 4.8.
Summary (updated)
-----------------
Fix a VLC crash by delaying object deletion to avoid invalid access by QtDBus
Description (updated)
-------
As described in the bug report when opening the file dialog, canceling it and exiting \
VLC causes the application to seg fault. The backtraces posted in the bug report \
shows that the crash happens somewhere in QtDBus and I get a similar backtrace when \
using v1.1.7 of this application.
When I looked into this issue what I discovered was that only KIO classes that \
register themselves with QtDBus cause the crash. I only found that out because fixing \
the crash in KIO::Scheduler by defering its deletion using deleteLater() did not \
prevent the application from still crashing on exit. However, the crash had moved to \
another location, KBookmarkManager. The only common thing between the crash at \
KBookmarkmanager and KIO::Scheduler was that in both cases the backtrace shows QtDBus \
attempting to invoke or access some method or slot in the object that was just \
destroyed. At this point I decided to check how many other classes in KIO register \
themselves with QtDBus and found only one more. I then applied the same changes to \
all three, defering the deletion of any object registered with QtDBus using \
QObject::deleteLater, and the crashing went away.
Anyhow, I have no idea why the crashes are only seen with this application. I was not \
able to duplicate the crash using the same sequences in another Qt only app, Arora or \
any of the other KDE applications I tried.
This addresses bug 234484.
http://bugs.kde.org/show_bug.cgi?id=234484
Diffs (updated)
-----
kio/bookmarks/kbookmarkmanager.cc d8a9cb7
kio/kio/fileundomanager.cpp f580c29
kio/kio/scheduler.cpp 6b36d9d
Diff: http://git.reviewboard.kde.org/r/100577/diff/diff
Testing
-------
Thanks,
Dawit Alemayehu
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This is an automatically generated e-mail. To reply, visit:
<a href="http://git.reviewboard.kde.org/r/100577/">http://git.reviewboard.kde.org/r/100577/</a>
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<div>Review request for kdelibs and Thiago Macieira.</div>
<div>By Dawit Alemayehu.</div>
<p style="color: grey;"><i>Updated Jan. 30, 2012, 6:35 a.m.</i></p>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Changes</h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: \
1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">Bring back an updated version of this patch since this crash can be \
reproduced using Qt 4.8.</pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Summary \
(updated)</h1> <table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" \
style="border: 1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">Fix a VLC crash by delaying object deletion to avoid invalid access by \
QtDBus</pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description \
(updated)</h1> <table width="100%" bgcolor="#ffffff" cellspacing="0" \
cellpadding="10" style="border: 1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">As described in the bug report when opening the file dialog, canceling \
it and exiting VLC causes the application to seg fault. The backtraces posted in the \
bug report shows that the crash happens somewhere in QtDBus and I get a similar \
backtrace when using v1.1.7 of this application.
When I looked into this issue what I discovered was that only KIO classes that \
register themselves with QtDBus cause the crash. I only found that out because fixing \
the crash in KIO::Scheduler by defering its deletion using deleteLater() did not \
prevent the application from still crashing on exit. However, the crash had moved to \
another location, KBookmarkManager. The only common thing between the crash at \
KBookmarkmanager and KIO::Scheduler was that in both cases the backtrace shows QtDBus \
attempting to invoke or access some method or slot in the object that was just \
destroyed. At this point I decided to check how many other classes in KIO register \
themselves with QtDBus and found only one more. I then applied the same changes to \
all three, defering the deletion of any object registered with QtDBus using \
QObject::deleteLater, and the crashing went away.
Anyhow, I have no idea why the crashes are only seen with this application. I was not \
able to duplicate the crash using the same sequences in another Qt only app, Arora or \
any of the other KDE applications I tried.</pre> </td>
</tr>
</table>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Bugs: </b>
<a href="http://bugs.kde.org/show_bug.cgi?id=234484">234484</a>
</div>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> \
(updated)</h1> <ul style="margin-left: 3em; padding-left: 0;">
<li>kio/bookmarks/kbookmarkmanager.cc <span style="color: \
grey">(d8a9cb7)</span></li>
<li>kio/kio/fileundomanager.cpp <span style="color: grey">(f580c29)</span></li>
<li>kio/kio/scheduler.cpp <span style="color: grey">(6b36d9d)</span></li>
</ul>
<p><a href="http://git.reviewboard.kde.org/r/100577/diff/" style="margin-left: \
3em;">View Diff</a></p>
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